Audio jack detection circuit

ABSTRACT

This document discusses, among other things, a detection system configured to identify a type of a pole of a four-pole audio jack using first and second comparators. The detection system can include a bias circuit configured to bias a detection input coupled to the pole, and first and second comparators configured to compare the detection input to respective first and second thresholds to provide an indication of the type of the pole.

CLAIM OF PRIORITY

This application is a continuation of and claims the benefit of priority under 35 U.S.C. §120 to Seth M. Prentice, U.S. patent application Ser. No. 13/189,480, titled “MIC/GND DETECTION AND AUTOMATIC SWITCH,” filed on Jul. 22, 2011, which is hereby incorporated by reference in its entirety.

BACKGROUND

Many mobile devices, such as mobile phones or other portable electronics, include audio jacks configured to receive external audio accessories having an audio plug. However, audio plugs can have varying configurations, which can create issues for headset manufacturers and end users, as manufacturers can be forced to build specific phone configurations based on region, and end users can be forced to use only specific accessories with their mobile device

FIGS. 1-2 illustrate generally two example four-pole audio jack configurations. FIG. 1 illustrates generally an example of a four-pole audio plug 101 in an open mobile terminal platform (OMTP) configuration including a left speaker (LSPKR) pole at pole-1, a right speaker (RSPKR) pole at pole-2, a microphone (MIC) pole at pole-3, and a ground (GND) pole at pole-4. FIG. 2 illustrates generally an example of a four-pole audio jack 102 in an American Standard configuration including a LSPKR pole at pole-1, a RSPKR pole at pole-2, a GND pole at pole-3, and a MIC pole at pole-4. In other examples, other configurations can be realized, for example, a three-pole audio plug with GND poles at both pole-3 and pole-4.

OVERVIEW

This document discusses, among other things, a detection system configured to identify a type of a pole of a four-pole audio jack using first and second comparators. The detection system can include a bias circuit configured to bias a detection input coupled to the pole, and first and second comparators configured to compare the detection input to respective first and second thresholds to provide an indication of the type of the pole.

This section is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

FIGS. 1-2 illustrate generally example four-pole audio jack configurations.

FIG. 3 illustrates generally an example audio jack detection switch.

FIG. 4 illustrates generally an example detection circuit.

FIGS. 5-6 illustrate generally example detection flow diagrams.

FIGS. 7-8 illustrate generally example output waveforms.

DETAILED DESCRIPTION

The present inventors have recognized, among other things, an audio jack detection switch for three or four-pole accessories that can detect the location of a ground (GND) pole and a microphone (MIC) pole on an audio plug coupled to the audio jack and automatically route the GND and MIC poles to the appropriate connection (e.g., GND, a MIC connection of an audio sub system, such as a codec, etc.), for example, without a separate selection input, allowing manufacturers and end users to freely use accessories with different pole configurations.

In an example, the audio jack detection switch can be configured to detect and validate that an audio plug has been coupled to an audio jack, to distinguish between three and four-pole audio plugs, to detect the polarity of the GND and MIC poles on a four-pole audio plug (e.g., using impedance measurements, etc.), and to automatically route the GND and MIC poles to the appropriate connections. In certain examples, because mobile devices can be required to operate in noisy environments, the audio jack detection switch can be configured to filter noise associated with mobile communications (e.g., Global System for Mobile Communication (GSM) noise, audio noise, etc.), such as when detecting or measuring audio plug impedance, which can eliminate errors in noisy environments.

FIG. 3 illustrates generally an example of a system 300 including a baseband processor 105 (e.g., of a mobile device), an audio sub system 110 (e.g., a codec), an audio jack detection switch 115, and an audio jack 120. In an example, the audio jack detection switch 115 can include an oscillator and logic 116, switch enable timing 117, a detection circuit 118, and a crosspoint switch 119 or one or more other switches. In an example, the audio jack 120 can include a four-pole audio jack configured to receive a three or four-pole audio plug or other audio accessory.

In an example, the audio jack 120 can include connections for each of the four poles, such as a left speaker (LSPKR) connection, a right speaker (RSPKR) connection, a pole-3 connection, and a pole-4 connection.

In certain examples, the audio jack detection switch 115 can be configured to detect and validate that an audio plug has been received by the audio jack 120, distinguish between three and four-pole audio plugs, and detect send/end key activation, such as described in the commonly assigned John R. Turner et al. U.S. patent application Ser. No. 13/188,778, entitled “Audio Jack Detection and Configuration,” filed on Jul. 22, 2011, which is hereby incorporated by reference in its entirety.

In an example, the audio jack detection switch 115 can be configured to detect what is connected to the pole-3 and pole-4 connections of the audio jack. In an example, the audio jack detection switch 115 can determine between various audio plug configurations, including at least one of:

-   -   1) a three-pole audio plug, with the pole-3 and pole-4 plugs         shorted (e.g., grounded);     -   2) a four-pole audio plug, with the pole-3 plug including a MIC         pole and the pole-4 plug including a GND pole;     -   3) a four-pole audio plug, with the pole-3 plug including a GND         pole and the pole-4 plug including a MIC pole;     -   4) floating or open connections at the pole-3 and pole-4 plugs;         or     -   5) one or more other configurations, such as a video connection.

After the detection or determination is complete, the audio jack detection switch 115 can be configured to automatically route the poles to the appropriate connection (e.g., the MIC pole to the MIC input of the audio sub system 110, the GND pole to a ground connection, such as at the audio jack detection switch 115, the audio sub system 110, the baseband processor 105, etc. In an example, after automatically switching or routing the poles to the appropriate connection, the audio jack detection switch 115 can be configured to enter a low power mode to reduce power consumption.

FIG. 4 illustrates generally an example of a system 400 including a detection circuit 118 including one or more comparators (e.g., first and second comparators 125, 126), a resistor 127 (e.g., 40KΩ, etc.), a switch 128, and a current source 129. In an example, the detection circuit 118 can be configured to detect or measure the impedance of the pole-3 and pole-4 connections of the audio jack by selectively coupling one of the GND/MIC1 or GND/MIC2 connections to the detection circuit 118.

In an example, the first and second comparators 125, 126 can include different threshold voltages (e.g., illustrated in FIG. 4 as 0.52*VDD and 0.1*VDD for the first and second comparators 125, 126, respectively, or one or more other threshold voltages). In certain examples, the threshold voltages can be selected or controlled to provide different detection stages. Further, the different threshold voltages coupled with the combination of the voltage source VDD and the current source 129, controllable using the switch 128, can provide multiple detection stages that can optimize current for detecting different loads (e.g., closing the switch 128 and using the combination of VDD and the current source 129 to detect the impedance on the GND/MIC1 or GND/MIC2 connection). Further, the high impedance DC measurement technique can minimize the pop & click in headphones or speakers.

In an example, the first and second comparators 125, 126 can be used to detect GSM noise, and to distinguish between GSM noise and audio noise. Generally, the first and second comparators 125, 126 can be monitored for state changes. If the state changes 3 clock cycles, a counter is incremented. If the state changes continue to change for a period of time (e.g., 100 mS), the counter can be compared to a specified range. In an example, the range can include between 34 and 54, which corresponds to the frequency of the GSM noise, or approximately 217 Hz. If GSM noise is determined, the audio jack detection switch can wait and start detection again. If the count is not within the range, it is assumed that the noise is audio noise, and that the audio jack includes a forward bias four-pole audio jack with pole-3 as the MIC pole.

FIG. 5 illustrates generally an example detection flow diagram 500 including detecting the impedance of audio plug poles (e.g., the GND and MIC poles on a four-pole audio plug, pole-3 and pole-4, etc.) and validating the detection (e.g., using a series of sequential detections, using different detection stages, etc.). If the detection is invalid or unknown, the impedance can be re-detected. In an example, if the detection is valid, the audio jack detection switch can automatically route the poles to the proper connections (e.g., the GND pole to a GND connection, the MIC pole to a MIC connection on the audio sub system, etc.) and enter an active low power state.

At 501, a baseband processor (e.g., the baseband processor 105) can provide an enable (EN) signal to an audio jack detection switch (e.g., the audio jack detection switch 115) and, at 502, a detection circuit (e.g., the detection circuit 118) can be turned on. In an example, the detection circuit can be triggered by detecting that the audio jack has received an audio plug.

At 503, a switch (e.g., the switch 128) in the detection circuit can be opened and closed. At 504, when the detection is complete, the state of the comparators (e.g., first and second comparators 125, 126) can be queried.

At 504, if the state of the connections is known, at 505, the audio jack detection switch can automatically route both the audio plug poles to the appropriate connection (e.g., GND, MIC, etc.), such as by using the crosspoint switch. At 506, an active low power state can be enabled. At 507, if the enable signal remains low for a specific time period, a disabled low power state can be entered, and process flow can return to step 501.

At 504, if the state of the connections is unknown, a counter can be incremented at 509. At 510, if the count is less than a first number (e.g., 2, etc.), the process can return to step 503. At 510, if the count is equal to the first number (e.g., 2, etc.), the audio jack detection switch can default to a three-pole audio plug and automatically route both of the pole-3 and pole-4 connections to GND.

FIG. 6 illustrates generally an example detection flow diagram 600 including detecting the impedance of audio plug poles. Generally, the switch coupling the current source to the detection circuit can be open to detect no connection or to determine if pole-3 and pole-4 are floating. To detect for MIC polarity or for a short, the switch can be closed.

At 601, a detection circuit can be turned on. At 602, the switch can be opened, and the audio jack detection switch can be configured to detect a float with a debounce of 1 mS. At 603, the sample is taken a predetermined number of times (e.g., three times) within a sample period, (e.g., tSAMPLE*0.5, tSAMPLE*0.75, tSAMPLE*1.0, etc.). At 604, if each of the predetermined number of samples are detected as floating, an active low power state can be entered at 618, and process flow can return to step 602. Generally, when a float is detected, the detection circuit can enter a low power mode for a specified time period (e.g., tPOLE). After the specified time period, the detection circuit can detect again. If a float is detected again, the low power mode loop can continue. If the detection is not float, the detection device can move on to test for a short or MIC polarity. If a float is ever detected, the detection device can default back to the low power state for the specified time period.

At 604, if each of the predetermined number of samples are not detected as floating after a period of time at 605, the audio jack can be detected at 606 as a four-pole audio jack and the switch can be closed.

At 607, variables “A” and “B” are set at an initial value and then compared, at 608, to the values of the first and second comparators. At 610, if there are no changes to the values of the first and second comparators, a high frequency count can be reset. At 611, if the values of the first and second comparators are still valid, then the detection is complete at 612. If the values of the first and second are not valid, process flow can return to step 607.

At 608, if the values of the first and second comparators changed, then at 609, the high frequency count can be incremented. At 613, if the high frequency count is less than a specified number (e.g., three, etc.), process flow can return to step 607. If the high frequency count is equal to the specified number, the values of variables “A” and “B” can be updated at 614 and a GSM count can be incremented at 615. At 616, process flow returns to step 607 until a time period is reached. During this period, if the values of the first and second comparators continues to change, the number of GSM count, representing GSM noise, can continue to increase.

At 617, once the timer has maxed out, the GSM count can be compared to a range, illustrated in FIG. 6 as greater than 34 but less than 54. In an example, this range can correspond to the approximate number of faults caused by GSM noise during the time period of step 616, or approximately 217 Hz. If the GSM count is not within the range, at 618 the noise at the comparator output must be audio noise, indicating a four-pole audio jack with a forward biased microphone and pole-3 corresponding to the MIC pole. At 619, detection is exited. At 617, if the GSM count is within the range, then GSM noise is causing the error, and process flow returns to step 618.

FIG. 7 illustrates generally an example comparator output 700 including a plurality of GSM noise occurrences 705, at approximately 217 Hz, the burst rate of the GSM transmission, causing the output of the comparator to change values, for example, at 710. In certain examples, the comparator changes can be counted, and GSM noise can be distinguished from audio noise by the number of occurrences during a specified time period.

FIG. 8 illustrates generally an example microphone audio output 800, including a microphone output 805. When a microphone is forward biased, the JFET type microphone can change impedance with audio noise. During detection, these impedance changes can cause the comparators to change states. This state change can pass the comparator voltage references, and the audio filter will identify when audio is present. Generally, the audio jack detection switch can identify audio noise from GSM noise by the frequency or total occurrences of the noise within a specified time period.

Additional Notes

In Example 1, a detection system includes a bias circuit configured to bias a detection input selectively coupled to a pole of a four-pole audio jack and first and second comparators configured to compare the detection input to respective first and second thresholds and to provide an indication of a type of the pole.

In Example 2, the four-pole audio jack of Example 1 optionally includes a ground (GND) pole and a microphone (MIC) pole, wherein the type of the pole includes a MIC pole or a GND pole.

In Example 3, the type of the pole of any one or more of Examples 1-2 optionally includes a MIC pole, a GND pole, or a floating pole.

In Example 4, the first and second comparators of any one or more of Examples 1-3 are optionally configured to provide an indication of an impedance at the pole.

In Example 5, any one or more of Examples 1-4 optionally include a switch configured to automatically couple the pole to a MIC connection of a processor or to automatically couple the pole to a GND connection using information from the first and second comparators.

In Example 6, the first threshold of any one or more of Examples 1-5 is optionally higher than the second threshold of any one or more of Examples 1-5 and the second threshold of any one or more of Examples 1-5 is optionally higher than GND, wherein the switch of any one or more of Examples 1-5 is optionally configured to couple the pole to the MIC connection of the processor when the detection input is between the first and second thresholds.

In Example 7, the first threshold of any one or more of Examples 1-6 is optionally higher than the second threshold of any one or more of Examples 1-6 and the second threshold of any one or more of Examples 1-6 is optionally higher than GND, wherein the switch of any one or more of Examples 1-6 is optionally configured to couple the pole to the GND connection of the processor when the detection input is above the first and second thresholds.

In Example 8, the first threshold of any one or more of Examples 1-7 is optionally higher than the second threshold of any one or more of Examples 1-7 and the second threshold of any one or more of Examples 1-7 is optionally higher than GND, wherein the switch is configured to couple the pole to the GND connection of the processor when the detection input is below the first and second thresholds.

In Example 9, the bias circuit of any one or more of Examples 1-8 optionally includes a bias resistor configured to receive a supply voltage.

In Example 10, the bias circuit of any one or more of Examples 1-9 optionally includes a bias resistor configured to receive a supply voltage, a current source, and a bias switch configure to selectively couple the current source to the detection input.

In Example 11, a detection method includes selectively coupling a pole of a four-pole audio jack to a detection input of a detection circuit, biasing the detection input using a bias circuit, comparing the detection input to first and second thresholds using respective first and second comparators, and identifying a type of the pole using the comparisons of the detection input to the first and second thresholds.

In Example 12, the four-pole audio jack of any one or more of Examples 1-11 optionally includes a ground (GND) pole and a microphone (MIC) pole, wherein the identifying the type of the pole of any one or more of Examples 1-11 optionally includes identifying the pole as a MIC pole or a GND pole.

In Example 13, the selectively coupling the pole of any one or more of Examples 1-12 optionally includes first, selectively coupling a first pole of the four-pole audio jack to the detection input to identify the first pole as the MIC pole or the GND pole, and second, separately selectively coupling a second pole of the four-pole audio jack to the detection circuit to identify the second pole as the MIC pole or the GND pole.

In Example 14, the biasing the detection input of any one or more of Examples 1-13 optionally includes biasing the detection input using a voltage source to determine no connection at the first pole and biasing the detection input using a current source to determine connection at the first pole.

In Example 15, the first threshold of any one or more of Examples 1-14 is optionally higher than the second threshold of any one or more of Examples 1-14 and the second threshold of any one or more of Examples 1-14 is optionally higher than GND, wherein the identifying the pole of any one or more of Examples 1-14 optionally includes identifying the pole as the MIC pole when the detection input is between the first and second thresholds.

In Example 16, the first threshold of any one or more of Examples 1-15 is optionally higher than the second threshold of any one or more of Examples 1-15 and the second threshold of any one or more of Examples 1-15 is optionally higher than GND, wherein the identifying the pole of any one or more of Examples 1-15 optionally includes identifying the pole as the GND pole when the detection input is above or below the first and second thresholds.

In Example 17, any one or more of Examples 1-16 optionally includes automatically coupling the identified pole to a MIC connection of a processor or to a GND connection of a processor using a switch.

In Example 18, a detection system includes a bias circuit configured to bias a detection input selectively coupled to a pole of a four-pole audio jack, the four-pole audio jack including a ground (GND) pole and a microphone (MIC) pole, first and second comparators configured to compare the detection input to respective first and second thresholds and to provide an indication of the pole as a MIC pole or a GND pole, and a switch configured to automatically couple the pole to a MIC connection of a processor or to automatically couple the pole to a GND connection using information from the first and second comparators.

In Example 19, the first threshold of any one or more of Examples 1-18 is optionally higher than the second threshold of any one or more of Examples 1-18 and the second threshold of any one or more of Examples 1-18 is optionally higher than GND, wherein the switch of any one or more of Examples 1-18 is configured to couple the pole to the MIC connection of the processor when the detection input is between the first and second thresholds.

In Example 20, the first threshold of any one or more of Examples 1-19 is optionally higher than the second threshold of any one or more of Examples 1-19 and the second threshold of any one or more of Examples 1-19 is optionally higher than GND, wherein the switch of any one or more of Examples 1-19 is optionally configured to couple the pole to the GND connection of the processor when the detection input is above or below the first and second thresholds.

In Example 21, a system or apparatus can include, or can optionally be combined with any portion or combination of any portions of any one or more of Examples 1-20 to include, means for performing any one or more of the functions of Examples 1-20, or a machine-readable medium including instructions that, when performed by a machine, cause the machine to perform any one or more of the functions of Examples 1-20.

The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, in an example, the code can be tangibly stored on one or more volatile, non-transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.

The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 

What is claimed is:
 1. A detection system, comprising: a bias circuit configured to bias a detection input selectively coupled to a pole of a four-pole audio jack; and first and second comparators configured to compare a value of the detection input to respective first and second thresholds and to provide an indication of a type of the pole, wherein the bias circuit includes: a bias resistor configured to receive a supply voltage; a current source; and a bias switch configure to selectively couple the current source to the detection input, wherein the current source and the bias switch are in parallel with the bias resistor.
 2. The system of claim 1, wherein the four-pole audio jack includes: a ground (GND) pole; and a microphone (MIC) pole; and wherein the type of the pole includes a MIC pole or a GND pole.
 3. The system of claim 1, wherein the type of the pole includes a MIC pole, a GND pole, or a floating pole.
 4. The system of claim 1, wherein the first and second comparators are configured to provide an indication of an impedance at the pole.
 5. The detection system of claim 1, including: a switch configured to automatically couple the pole to a MIC connection of a processor or to automatically couple the pole to a GND connection using information from the first and second comparators.
 6. The detection system of claim 5, wherein the first threshold is higher than the second threshold and the second threshold is higher than GND; and wherein the switch is configured to couple the pole to the MIC connection of the processor when the value of the detection input is between the first and second thresholds.
 7. The detection system of claim 5, wherein the first threshold is higher than the second threshold and the second threshold is higher than GND; and wherein the switch is configured to couple the pole to the GND connection of the processor when the value of the detection input is above the first and second thresholds.
 8. The detection system of claim 5, wherein the first threshold is higher than the second threshold and the second threshold is higher than GND; and wherein the switch is configured to couple the pole to the GND connection of the processor when the value of the detection input is below the first and second thresholds.
 9. The detection system of claim 1, wherein the bias circuit includes: a bias resistor configured to receive a supply voltage.
 10. A detection method, comprising: selectively coupling a pole of a four-pole audio jack to a detection input of a detection circuit; biasing the detection input using a bias circuit; comparing a value of the detection input to first and second thresholds using respective first and second comparators; and identifying a type of the pole using the comparisons of the value of the detection input to the first and second thresholds, wherein the bias circuit includes: a bias resistor configured to receive a supply voltage; a current source; and a bias switch configured to selectively couple the current source to the detection input, wherein the current source and the bias switch are in parallel with the bias resistor.
 11. The detection method of claim 10, wherein the four-pole audio jack includes: a ground (GND) pole; and a microphone (MIC) pole; and wherein the identifying the type of the pole includes identifying the pole as a MIC pole or a GND pole.
 12. The detection method of claim 10, wherein the selectively coupling the pole includes: first, selectively coupling a first pole of the four-pole audio jack to the detection input to identify the first pole as the MIC pole or the GND pole; and second, separately selectively coupling a second pole of the four-pole audio jack to the detection circuit to identify the second pole as the MIC pole or the GND pole.
 13. The detection method of claim 10, wherein the biasing the detection input includes: biasing the detection input using a voltage source to determine no connection at the first pole; and biasing the detection input using a current source to determine connection at the first pole.
 14. The detection method of claim 10, wherein the first threshold is higher than the second threshold and the second threshold is higher than GND; and wherein the identifying the pole includes identifying the pole as the MIC pole when the value of the detection input is between the first and second thresholds.
 15. The detection method of claim 10, wherein the first threshold is higher than the second threshold and the second threshold is higher than GND; and wherein the identifying the pole includes identifying the pole as the GND pole when the value of the detection input is above or below the first and second thresholds.
 16. The detection method of claim 10, including: automatically coupling the identified pole to a MIC connection of a processor or to a GND connection of a processor using a switch.
 17. The detection method of claim 10, wherein the identifying the type of the pole includes identifying the pole as a MIC pole, a GND pole, or a floating pole.
 18. A detection system, comprising: a bias circuit configured to bias a detection input selectively coupled to a pole of a four-pole audio jack, the four-pole audio jack including: a ground (GND) pole; and a microphone (MIC) pole; first and second comparators configured to compare a value of the detection input to respective first and second thresholds and to provide an indication of the pole as a MIC pole or a GND pole; and a switch configured to automatically couple the pole to a MIC connection of a processor or to automatically couple the pole to a GND connection using information from the first and second comparators, wherein the bias circuit includes: a bias resistor configured to receive a supply voltage; a current source; and a bias switch configure to selectively couple the current source to the detection input, wherein the current source and the bias switch are in parallel with the bias resistor.
 19. The detection system of claim 18, wherein the first threshold is higher than the second threshold and the second threshold is higher than GND; and wherein the switch is configured to couple the pole to the MIC connection of the processor when the value of the detection input is between the first and second thresholds.
 20. The detection system of claim 18, wherein the first threshold is higher than the second threshold and the second threshold is higher than GND; and wherein the switch is configured to couple the pole to the GND connection of the processor when the value of the detection input is above or below the first and second thresholds. 